Safety device



Aug 7, 1945- E. E. GROVER 2,380,964

SAFETY DEVI CE Filed June 50, 1943 F|G 2 FIG 5 WITNESSES: INVENTOR El//btt E. Grof/er ATTORN Y `at all points of the surface.

Patented ug. 7, 1945 assos ssra'rv nEvlcE .Emea E. Grover, springend, man.. ungemu Westinghouse Electric Corporatiomalt Pittsburgh, Pa., a corporation of Pennsylvania Application June 30, 1943, Serial No. 492,808 Claims. (01.22049) This invention relates to safety devices and more particularly to safety devices adapted to rupture when the pressure within the vessel to which they are applied exceeds a predetermined amount.

An object of the invention is to provide a safety device in which the stresses created by excessive pressure in the container or vessel may be localized at a specinc point or points on the surface of the safety device.

For convenience in manufacturing and in its application to pressure vessels, I prefer to make the device in the form of a disc and it will be hereafter so described, but such construction 4is -not essential in carrying out my invention.

Safety discs made of a rupturable metallic membrane are, of course, well known. However, when such devices, made in the form of a simple disc, are subjected to pressure, they tend to as sume a spherical shape and .are stressed equally Thus, when the pressure exceeds the limit, the disc ruptures indiscriminately and sometimes forms dangerous flying fragments. VThe control overI the rupture f pressure is not at all critical and the operation is so indeterminate that it cannot be said to be responsive `to a predetermined pressure condition.

My invention, on the other hand, provides a means for so localizing the pressure eect on a specific point or points of the safety device, that the rupture pressure can be controlled within fairly close limits.

These and other objects are effected by my invention as will be apparent from the following description and claims taken in connection with the accompanying drawing, forming a part of this application, in which:

vessel. The dispenser is designed to contain volatile fluid such as dichiorodiiluoromethane which serves as-alpropellant for discharins another uid, ordinarily nonvolatile. into' the atmosphere through a capillary tube I2 extending from a point adjacent the bottom wall Il of the container, through a nipple I4 to which it is hermetically bonded andhaving an outlet end l5 disposed outside the container. The outlet end is Fig. 1 is a vertical section through a pressure vessel to which my safety device is applied;

Fig. 2 is a bottom view of the vessel of Fig. l. showing the safety device in operative position; Fig. 3 is an enlarged plan view of the safety device alone:

F18. 4 is a. section taken on line IV-IV of Fis. 3; 1

Fig. 5 is a vertical section through a portion of a pressure vessel, showing an alternative manner of 'applying the safety device:

Fig. 6 isa vertical section through a disc. embodying my invention in another form; and

Fig. 'I'isaplanview ofthediscshowninFig. 6.

The pressure vessel illustrated in Fig. 1 comprises a dispenser A of the type disclosed and claimed in the copending application of William B. Anderson, Serial NG. 458,555, med August 23 1942, and assigned to Westinghouse Electric fr Manufacturing Company. It comprises a pair of metal lshells Il and ii metallically bonded at their juncture to provide a hermetically-seaied sealed, as at II, by a crimping operation or otherwise after the container has been charged. When the charge is to be dispensed, .the capillary tube is broken of! above the nipple Il. A cap (not shown) may be provided to be screwed onto the nipple i4 to provide a temporary seal for the tube and container.

1t is desirable that sealed vesseiser this character, having a volatile content such as liquids which vaporize at normal temperatures. and which may be subjected to such conditions of shipping' and storage that' their temperature and pressure rise rapidly, be provided with some safety device which will release the contents when the pressure inside the vessel has reached some predetermined range. A

' As I lhave stated before, it has heretofore been proposed to provide pressure relief devices for pressure vessels. Such devices have taken the form of a frangible disc, a fusible plug, or a spring-pressed valves So far as I am aware, the discs heretofore employed have been either flat or 'convex with the result that pressure applied to their surface is distributed equally over the surface thereof. If the predetermined blow-off pressure is relatively low, the disc must be made of metal so thin that it will not stand ordinary handling and use. Further, such discs tend to rup'- ture with a large, jagged-edged hole or else to explode into fragments, creating a hazard.

I have found, however, that if a disc is so constructed that the stresses are localized on one or more predetermined points, I may make the disc of a material heavy enough to withstand ordinary use and yet which will rupture within a predetermined pressure range to relieve the contents of the vessel.

A preferred embodiment of the invention shown in Figs. 1 to 5, inclusive, comprises a thin metal disc 20 having embossed thereon a raised and generally convex portion in the form of a clover leaf 2|. The disc is also` preferably embossed near its center with 'a raised circle 22. 'I'he disc may be applied to the vessel or container by brazing it into a recess 23 formed in the bottom wall il of the container, said recess being sumciently deep to receive the entire disc and the flat wall portion 2l of the recess thus affording a hermetic seal between the disc and the container. Access between the interior of the container and the rupture disc is provided by an orifice 2l formed in the wall portion 2i of therecess 23.

I have found that the size of the port Il is rather critical, in that it must be sumciently large to allow the release of the container at a rate sumciently fast to relieve the pressure before the vessel itself explodes, but not so large that the discharge from the vessel will cause the vessel to jump violently. For example. I have found that in a container having a capacity of slightly over one pound of liquid dichlorodiiiuoromethane and containing approximately one pound of that compound, and in which the container itself will explode at or near a pressure of 2,000 pounds per square inch, and which container is provided with a disc adapted to rupture at from '100 to 825 pounds per square inch, the orifice 2l should be approximately one-sixteenth I of an inch in diameter.

'I'he embossed circle portion 22 serves as`an arch to maintain the. center portion of the disc away from the orifice 26 during the brazing operation. ,Otherwise the raised portion of the disc would sag and become brazed to the wall portion 2l, and materially alter the operating characteristics of the device.

The gist of my invention lies in the provision of the stress points Il formed at the juncture of each pair of lobes I I When an excessive pres,- sure develops inside the vessel, these convergent points bear localized stresses which cause a rupture of the disc at at least one of these points, and a tearing of the disc from this point toward the center. The area of disc surface exposed to pressure and the weight and quality of the metal used in making the disc are important in determining the rupture pressure. but these are controllable factors applicable to any type of safety disc.

Obviously, the disc, according to my invention, need not be shaped like a clover leaf. Any stamping or embossing which will provide one or more indentations'awsy from the periphery of the embossing and toward the center will serve equally well. A` single indentation, for example,

would provide a generally heart-shaped embossing. The clover leaf design. however, provides three stress points as, a safety factor.

Neither is it necea-ry that the disc itself be embossed. In Figs. 6 and '1, I have shown an embodiment of the invention in which a metal disc.

the safety disc Ilj-to a pressure vessel by clamp-- ing it between a screw-threaded boss u attached to the pressure vessel as by welding, and an internally threaded cap 4l. Gaskets 41 are preferably provided to form a fiuidtight Joint. Buch a structure would be particularly applicable where the safety device is used on permanent or renllable containers. auch as water or steam boilers. and similar containers where provision for replacement ofthe safety device should be made.

It will be apparent from the foregoing description that my invention provides a safety device having a noncircular area exposed to pressure and having localized stress points which rupture under a predetermined pressure.

While I have shown specific embodiments of my invention, it. will be obvious to those skilled in the art that it is not solimited, but is susceptible of various other changes and modincations without departing from the spirit thereof. and I desired, therefore, that only such limitations sh'all be placed thereupon as are specifically set forth in the appended claims.

What I claim is:

1. A safety device ruptura'ble upon'the application of a predetermined pressure, said device,

comprising a thin metallic membrane of uniform thickness having a portion only of its area exposed to a pressure source, said exposed portion being non-circular in outline and having at least one radial indentation between its outermost exposed edge and its center providing a point where the stresses produced by the pressure source are concentrated.

2. A device according to the preceding claim wherein the center of the membrane has a circular embossing to reinforce the membrane.

3. A device according to claim l wherein the non-circular exposed portion has substantially the shape of a clover leaf.

4. In combination, a closed vessel adapted to contain a fluid. means associated with said vessel for relieving excessive pressure generated therein, s'aid means comprising a thin metal membrane of uniform thickness sealed at its periphery to said vessel, the remainder of said membrane being noncircular in outline and being exposedto the pressure generated in said vessel. a wall of said vessel having therein an orifice 'of predetermined diameter providing communication between the interior of said vessel and the inner side of said membrane, said membrane being provided with indentations extending inwardly from the periphery of a circle circumscribing the outer edge of'the exposed area toward its center to provide rupturable stress points,

5. In combination, a closed vessel adapted to contain auid, means associated with said vessel for relieving excessive pressure generated therein, a wall of said vessel vbeing provided with! a recess for receiving' said means, said means comprising a thin metal membrane of uniform thickness sealed at its periphery to said vessel within said recess, the remainder of said mem-4 -brane being substantially convex and being exl ELLIO'I'I E. GRQVRR. 

